Anticholinergic (AC) drugs cause cognitive impairment. If you already have cognitive impairment, they cause it to get worse. I wrote about a study a few years ago that found cognitively normal people who took at least one anticholinergic drug developed cognitive impairment. From that study: “The use of AC medication was associated with increased brain atrophy and dysfunction and clinical decline.”

Here’s yet another study – from last week. Again, none of these participants had any cognitive or memory problems before the study.
Press Release: Common Class Of Drugs Linked To Increased Risk Of Alzheimer’s Disease.

Participants with AD biomarkers who were taking anticholinergic drugs were four times more likely to develop MCI* than persons lacking biomarkers and not taking the drugs.

Persons at genetic risk for AD who took anticholinergic drugs were approximately 2.5 times more likely to develop MCI than those without genetic risk factors and who were not taking the drugs.

* MCI: mild cognitive impairment, “often a precursor to dementia and Alzheimer’s disease”

Study: Association Of Anticholinergic Medication And Alzheimer’s Disease (AD) Biomarkers With Incidence Of Mild Cognitive Impairment (MCI) Among Cognitively Normal Older Adults, Neurology, 2 September 2020

Conclusions: Anticholinergic medications (aCH) increased risk of incident MCI and cognitive decline, and effects were significantly enhanced among individuals with genetic risk factors and cerebrospinal fluid (CSF)-based AD pathophysiological markers. Findings underscore the adverse impact of aCH medications on cognition and the need for deprescribing trials, particularly among individuals with elevated risk for AD.

What are anticholinergic drugs?

They work by blocking acetylcholine — a type of neurotransmitter or chemical messenger known to be critical for memory function — from binding to receptors on certain nerve cells. The effect is to inhibit parasympathetic nerve impulses, which are involved in a variety of involuntary muscle movements, such as those in the gastrointestinal tract and lungs, and bodily functions like salivation, digestion and urination.

There are many AC drugs. Here’s a list that I picked up from VirginiaGeriatrics.org a few years ago:

Commonly used drugs with moderate to high anticholinergic properties:

Antiarrythmics:
Disopyramide – Norpace®
Procainamide – Pronestyl®
Quinidine – Quinaglute®, Quinidex®

Antiemetics:
Dimenhydrinate – Dramamine®
Meclizine – Antivert®, Bonine®
Trimethobenzamide – Tigan®
Prochlorperazine -Compazine®

Antihistamines:
Azatadine – Optimine®
Chlorpheniramine – Chlor-Trimeton®
Clemastine – Tavist®
Diphenhydramine – Tylenol PM®, Sominex®, Benadryl®
Hydroxyzine – Atarax®, Vistaril®
Promethazine – Phenergan®

Antiparkinson Agents:
Benztropine – Cogentin®
Biperiden – Akineton®
Procyclidine – Kemadrin®
Trihexyphenidyl – Artane®

Antipsychotics:
Chlorpromazine – Thorazine®
Clozapine – Clozaril®
Mesoridazine – Serentil®
Olanzapine – Zyprexa®
Promazine – Sparine®
Quetiapine – Seroquel®
Thioridazine – Mellaril®

Antispasmotics:
Atropine – Sal-Tropine®
Belladonna alkaloids – Donnatal®, Bellatal®, Barbidonna®
Dicyclomine – Antispas®, Bentyl®
Flavoxate – Urispas®
Hyoscyamine – Anaspaz®, Levbid®, Cystospaz®, Levsin/SL®
Oxybutynin – Ditropan®
Scopolamine
Tolterodine – Detrol®

Skeletal muscle relaxants:
Carisoprodal – Soma®
Chlorzoxazone – Parafon®, Forte®
Cyclobenzaprine – Flexeril®
Methocarbamol – Robaxin®
Orphenadrine – Norflex®

Tricyclic Antidepressants:
Amitriptyline – Elavil®
Desipramine – Norpramin®
Doxepin – Sinequan®
Imipramine – Tofranil®
Nortriptyline -Aventyl®, Pamelor®

It’s not an exhaustive list. There are more antidepressants, sleep aids, drugs for asthma and chronic bronchitis, antacids like Zantac, allergy and cold meds, diuretics, drugs for bladder control, even eye drops like Atropine used to dilate pupils. Many can be purchased over-the-counter, without a prescription.

A Pocket Guide (click to enlarge):

That anticholinergic drugs cause structural and functional changes in the brain – of healthy people – and increase the risk for dementia and Alzheimer’s doesn’t get the airtime it should because … look at all these drugs! Drug companies sponsor airtime. They would be digging their own graves. And if people develop Alzheimer’s? No problem; there will be a drug for that too. This is what happens when industries, especially high-profit industries like pharmaceuticals, have too large an influence on regulatory bodies.

Related:
‘Strongest Evidence Yet’ Links Anticholinergic Drugs, Dementia, Medscape, January 2015

Cumulative Use Of Strong Anticholinergics And Incident Dementia, A Prospective Cohort Study, JAMA Internal Medicine, March 2015

Drugs With Anticholinergic Properties, Cognitive Decline, and Dementia in an Elderly General Population, The 3-City Study, JAMA Internal Medicine, July 2009